Even if he doesn't know it, most kids grades are merely representative of their knowledge of technique (usually simplified ones at that), and have little or nothing to do with their philosophies or attitudes. It doesn't pay to worry about it, as that student's deportment on the mat is a matter for the instructor's attention, not yours. Eventually, there will be an "adjustment", one way or another. Don't let yourself be drawn into a comparison of ranks. Belts are just to hold your pants up, anyway.